Synergistic microbicidal combinations containing 2-n-octyl-3-isothiazolone and certain commercial biocides

ABSTRACT

Synergistic antimicrobial and biocidal compositions comprising 2-n-octyl-4-isothizolin-3-one and one or more known biocides for more effective, and broader control of miccroorganisms in various industrial systems are disclosed.

This is a divisional of application Ser. No. 322,455, filed Mar. 10, 1989, now U.S. Pat. No. 4,964,892.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to synergistic antimicrobial or biocidal compositions including an isothiazolone and one or more of known biocides for more effective and broader control of micro-organisms in various industrial systems and for household products, agricultural products, and biomedical products, etc. In particular, the present invention relates to the use of a composition of 2-n-octyl-4-isothiazolin-3-one (also known as 2-n-octyl-3-isothiazolone or 2-n-octylisothiazolone) with one or more of the following 21 compounds: 2-(hydroxymethyl)amino-2-methylpropanol; 2-(hydroxymethyl)aminoethanol; 5-bromo-5-nitro-1,3-dioxane; hexahydro-1,3,5-triethyl-s-triazine; α-benzoyl-α-chloroformaldoxime; benzylbromoacetate; p-chloro-m-xylenol; bis-(2-hydroxy-5-chlorophenyl)sulfide; p-tolyldiiodomethylsulfone; 3-iodo-2-propynylbutylcarbamate; 5-hydroxypoly(methyleneoxy)-methyl-1-aza-3,7-dioxabicyclo(3,3,0)octane; dipropylamine ether; dodecylamine; N-(hydroxymethyl)-N'-(1,3-di(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl)-N'-(hydroxymethyl)urea; 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride; 1,2-dibromo-2,4-dicyanobutane; N,N-dimethyl-N'-phenyl-N'-(fluorodichloromethylthio)sulfamide; N,N'-di(hydroxmethyl)-5,5'-dimethylhydantoin; 2-bromo-2-nitropropanediol; methylene-bis-thiocyanate; and 2,4-dichlorobenzyl alcohol.

2. Prior Art

The isothiazolones are described in U.S. Pat. Nos. 3,761,488; 4,105,431; 4,252,694; 4,265,899 and 4,279,762, and elsewhere. The 2-n-octyl-4-isothiazolin-3-one (octhilinone) is a superior fungicide with relatively lower activity against Gram-negative bacteria. The low activity against Gram negative bacteria has limited its uses in industrial systems where both bacteria and fungi are fouling the systems. To control these situations requires a higher concentration of octhilinone, which increases the cost of the treatment. Therefore, it is useful to find compositions which are more effective and exert broader control.

It has been discovered that compositions formed from 2-n-octyl-4-isothiazolin-3-one and one or more of the 21 specified compounds (supra) within specified range of ratios unexpectedly afforded synergistic antimicrobial activity against a wide range of microorganisms. The synergy in which the disruptive action on the organisms by the two compounds together is greater than the sum of both compounds taken alone does not arise from the expected activity of the components or from the expected improvement in activity. As a result of the synergy, the effective dose which can be lowered is not only more economical but also increases safety margin. The synergistic compositions provide more effective and broader control of microorganisms in a number of industrial systems.

It is the principal object of this invention to provide the use of synergistic compositions which overcome the disadvantages of the known biocidal compositions.

Important applications of the synergistic antimicrobial compositions of the present invention include but are not limited to: inhibiting the growth of bacteria and fungi in aqueous paints and coatings, adhesives, sealants, latex emulsions, and joint cements; preserving wood; preserving cutting fluids, controlling slime-producing bacteria and fungi in pulp and papermills and cooling towers; as a spray or dip treatment for textiles and leather to prevent mold growth; protecting paint films, especially exterior paints, from attack by fungi which occurs during weathering of the paint film; protecting processing equipment from slime deposits during manufacture of cane and beet sugar; preventing microorganism buildup and deposits in air washer or scrubber systems and in industrial fresh water supply systems; preserving fuel; controlling microorganisms contamination and deposits in oil field drilling fluids and muds, and in secondary petroleum recovery processes; preventing bacterial and fungal growth in paper coatings and coating processes; controlling bacterial and fungal growth and deposits during the manufacture of various specialty boards, e.g., carboard and particle board; preventing sap stain discoloroation on freshly cut wood of various kinds; controlling bacterial and fungal growth in clay and pigment slurries of various types; as a hard surface disinfectant to prevent growth of bacteria and fungi on walls, floors, etc.; as a preservative for cosmetic and toiletry raw materials, floor polishes, fabric softeners, household and industrial cleaners; in swimming pools to prevent algae growth; inhibiting the growth of harmful bacteria, yeasts, fungi on plants, trees, fruits, seeds, or soil; preserving agricultural formulations, electrodeposition systems, diagnostic and reagent products, medical devices; protecting animal dip compositions against the buildup of microorganisms, and in photoprocessing to prevent buildup of microorganisms, and the like.

The synergistic compositions of the invention may be added separately to an industrial system or may be formulated as a simple mixture comprising its essential ingredients, and if desired a suitable carrier or solvent, or as an aqueous emulsion or dispersion.

SUMMARY OF THE INVENTION

Compositions of octhilinone and one or more of the following compounds when employed at specified range of ratios exhibit synergistic biocidal and antimicrobial activity against a wide range of microorganisms: 2-(hydroxymethyl)amino-2-methylpropanol; 2-(hydroxymethyl) aminoethanol; 5-bromo-5-nitro-1,3-dioxane; hexahydro-1,3,5-triethyl-s-triazine; α-benzoyl-α-chloroformaldoxime; benzylbromoacetate; p-chloro-m-xylenol; bis-(2-hydroxy-5-chlorophenyl)sulfide; p-tolyldiiodomethylsulfone; 3-iodo-2-propynylbutylcarbamate; 5-hydroxypoly(methyleneoxy)-methyl-1-aza-3,7-dioxabicyclo(3,3,0)octane; dipropylamine ether; dodecylamine; N-(hydroxymethyl)-N'-(1,3-di(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl)-N'-(hydroxymethyl)urea; 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride; 1,2-dibromo-2,4-dicyanobutane; N,N-dimethyl-N'-phenyl-N'-(fluorodichloromethylthio)sulfamide; N,N'-di(hydroxymethyl)-5,5-dimethylhydantoin; 2-bromo-2-nitropropanediol; methylene-bis-thiocyanate; and 2,4-dichlorobenzyl alcohol.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention also relates to a method of inhibiting the growth of bacteria, fungi or algae in a locus subject to contamination by bacteria, fungi or algae, which comprises incorporating into or onto the locus in an amount which is effective to adversely affect the growth of bacteria, fungi or algae one or more of the synergistic combinations described above.

The composition of the invention can be formulated as a solution in water. While the amount of the instant composition in the formulated solution can vary over a wide range, the solutions can conveniently be formulated to contain from about 20 to about 400 ppm of the composition in solution, with the preferred range being from about 25 to 200 ppm of the composition. In formulating the solutions, other solvents which are water-miscible, such as ethyl alcohol, propyl alcohol, isopropyl alcohol, diethylene glycol, dipropylene glycol, polyethylene glycol, diethylene glycol, ethyl ether, and the like, may be employed in order to aid in solubilizing the active components. Furthermore, various other conventional additives may be employed, such as surfactants, dispersing agents, corrosion inhibitors, and the like.

In general, the ratio of the first component to second component is in the range of from about 150:1 to about 1:400. The other specific and preferred ratios are given in the examples.

The synergism of these two-components compositions is demonstrated by testing a wide range of concentrations and ratios of compounds, generated by two-fold serial dilutions in a liquid growth medium of a biocide in one dimension and another biocide in the second dimension, against a bacterium Escherichia coli (ATCC 11229) or a fungus Candida albicans (ATCC 11651), or a mixed culture of bacteria and fungi which are natural contaminants of a metalworking fluid. Each test tube was inoculated to about 2×10⁷ bacteria per ml or 2×10⁶ fungi per ml. The lowest concentrations of each compound or mixtures to inhibit visible growth (turbidity) at 37° for E. coli and at 30° C. for C. albicans, or the mixed culture for over 2 days is the minimum inhibitory concentration (MIC). The lowest concentration of each compound or the mixtures to kill 99.99% of fungi or 99.999% of bacteria after certain period of exposure from 1 day to 7 days is taken as minimum biocidal concentration (MBC). Both MIC and MBC are taken as end points of activity. End points for the mixtures of compound A and compound B were then compared with the end points for compound A alone and compound B alone. Synergism was determined by a commonly used and accepted method described by Kull, F. C.; Eisman, P. C.; Sylwestrowicz, H. D. and Mayer, R. L., in applied Microbiology 9:538-541 (1961) using the ratio determined by

    Qa/QA+Qb/QB=Synergy Index (SI)

wherein

QA=concentration of compound A in parts per million (ppm), acting alone, which produced an end point.

Qa=concentration of compound A in ppm, in the mixture, which produced an end point.

QB=concentration of compound B in ppm, acting alone, which produced an end point.

Qb=concentration of compound B in ppm, in the mixture, which produced an end point

when the sum of Qa/QA and Qb/QB is greater than one, antagonism is indicated. When the sum is equal to one additivity is indicated, and when less than one synergism is demonstrated.

The test results for demonstration of synergism of biocide combinations are shown in Table 1 through Table 21. Each table is organized to show:

1. the specific combination of compound A and compound B;

2. test against E. coli or C. albicans, or a mixed culture of bacteria and fungi;

3. test medium by either trypticase soy broth (TSB) or a minimal salt medium+0.2% glucose (M9G);

4. the method of evaluation by either MIC or MBC. The MBCId means MBC determined after 1-day exposure to biocides. MBC2d means MBC determined after 2-days exposure to biocides, etc.;

5. the end-point activity in ppm measured by MIC or MBC for compound A alone (QA), for compound B alone (QB), for compound A in the mixture (Qa), or for compound B in the mixture (Qb);

6. the calculation for synergy index (SI) based on the formula SI=Qa/QA+Qb/QB, and for the ratio of compound A to compound B in the synergistic combinations (Qa:Qb);

7. the range of ratios for synergism and the preferred ratios.

                                      TABLE 1                                      __________________________________________________________________________     Combination of Octhilinone and 2-(Hydroxymethyl)amino-2-                       methylpropanol                                                                 Method of                                                                            end-point activity in ppm                                                                         calculations                                          evaluation                                                                           QA  QB    Qa  Qb   Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                      __________________________________________________________________________     test against C. albicans in TSB medium                                         MIC    2.5                                                                               1000.0                                                                               1.3 500.0                                                                               0.50                                                                               0.50                                                                               1.00                                                                               1:400                                     test against E. coli in M9G medium                                             MIC   125.0                                                                              62.0  2.0 31.0 0.02                                                                               0.50                                                                               0.52                                                                               1:16                                            125.0                                                                              62.0  8.0 16.0 0.06                                                                               0.26                                                                               0.32                                                                              1:2                                              125.0                                                                              62.0  62.0                                                                                8.0 0.50                                                                               0.13                                                                               0.63                                                                              8:1                                        MBCId 250.0                                                                              250.0 16.0                                                                               31.0 0.06                                                                               0.12                                                                               0.19                                                                              1:2                                              250.0                                                                              250.0 31.0                                                                               16.0 0.12                                                                               0.06                                                                               0.19                                                                              2:1                                              250.0                                                                              250.0 62.0                                                                                8.0 0.25                                                                               0.03                                                                               0.28                                                                              8:1                                        MBC4d 125.0                                                                              62.0  2.0 31.0 0.02                                                                               0.50                                                                               0.52                                                                               1:16                                            125.0                                                                              62.0  8.0 16.0 0.06                                                                               0.26                                                                               0.32                                                                              1:2                                              125.0                                                                              62.0  62.0                                                                                8.0 0.50                                                                               0.13                                                                               0.63                                                                              8:1                                        MBC7d 125.0                                                                              62.0  2.0 31.0 0.02                                                                               0.50                                                                               0.52                                                                               1:16                                            125.0                                                                              62.0  8.0 16.0 0.06                                                                               0.26                                                                               0.32                                                                              1:2                                        __________________________________________________________________________      Compound A = Octhilinone                                                       Compound B = 2(Hydroxymethyl)amino-2-methylpropanol                            The synergistic ratios of compound A:compound B range from 8:1 to 1:16.        The preferred ratios are 1:2 to 1:16.                                    

                                      TABLE 2                                      __________________________________________________________________________     Combination of Octhilinone and 2-(Hydroxymethyl)aminoethanol                   Method of                                                                            end-point activity in ppm                                                                         calculations                                          evaluation                                                                           QA  QB    Qa  Qb   Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                      __________________________________________________________________________     test against E. coli in M9G medium                                             MIC   125.0                                                                              62.0  4.0 31.0 0.03                                                                               0.50                                                                               0.53                                                                              1:8                                              125.0                                                                              62.0  62.0                                                                                8.0 0.50                                                                               0.13                                                                               0.63                                                                              8:1                                        MBCId 250.0                                                                              500.0 62.0                                                                               16.0 0.25                                                                               0.03                                                                               0.28                                                                              4:1                                        MBC4d 125.0                                                                              62.0  4.0 31.0 0.03                                                                               0.50                                                                               0.53                                                                              1:8                                              125.0                                                                              62.0  62.0                                                                                8.0 0.50                                                                               0.13                                                                               0.63                                                                              8:1                                        MBC7d 125.0                                                                              62.0  4.0 31.0 0.03                                                                               0.50                                                                               0.53                                                                              1:8                                              125.0                                                                              62.0  62.0                                                                                8.0 0.50                                                                               0.13                                                                               0.63                                                                              8:1                                        test against C. albicans in TSB medium                                         MIC    1.3                                                                               1000.0                                                                               0.6 31.0 0.50                                                                               0.03                                                                               0.53                                                                               1:50                                      MBCId  1.3                                                                               1000.0                                                                               0.6 125.0                                                                               0.50                                                                               0.13                                                                               0.63                                                                               1:200                                     MBC4d  1.3                                                                               1000.0                                                                               0.6 125.0                                                                               0.50                                                                               0.13                                                                               0.63                                                                               1:200                                     __________________________________________________________________________      Compound A =  Octhilinone                                                      Compound B = 2(Hydroxymethyl)aminoethanol                                      The synergistic ratios of compound A:compound B range from 8:1 to 1:200.       The preferred ratios are 1:8 to 8:1                                      

                                      TABLE 3                                      __________________________________________________________________________     Combination of Octhilinone and 5-Bromo-5-nitro-1,3-dioxane                     Method of                                                                            end-point activity in ppm                                                                           calculations                                        evaluation                                                                           QA   QB   Qa    Qb   Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                    __________________________________________________________________________     test against E. coli in TSB medium                                             MBC   125.0                                                                               50.0 16.0  25.0 0.13                                                                               0.50                                                                               0.63                                                                              1:1.6                                    MBC   125.0                                                                               50.0 2.0   25.0 0.02                                                                               0.50                                                                               0.52                                                                              1:1.25                                   test against C. albicans in TSB medium                                         MIC    2.0 25.0 0.5   3.1  0.25                                                                               0.12                                                                               0.37                                                                              1:6.2                                           2.0 25.0 1.0   0.1  0.50                                                                               0.00                                                                               0.50                                                                              10:1                                     MBC2d  2.0 25.0 1.0   0.4  0.50                                                                               0.02                                                                               0.52                                                                              25:1                                     MBC6d  2.0 25.0 1.0   0.8  0.50                                                                               0.03                                                                               0.53                                                                              1.2:1                                    test against E. coli in M9G medium                                             MIC   125.0                                                                               10.0 62.0  0.6  0.50                                                                               0.06                                                                               0.56                                                                              100:1                                          125.0                                                                               10.0 16.0  2.5  0.13                                                                               0.25                                                                               0.38                                                                              6.4:1                                          125.0                                                                               10.0 2.0   5.0  0.02                                                                               0.50                                                                               0.52                                                                              1:2.5                                    MBCId 125.0                                                                               20.0 62.0  0.6  0.50                                                                               0.03                                                                               0.53                                                                              100:1                                          125.0                                                                               20.0 31.0  2.5  0.25                                                                               0.13                                                                               0.37                                                                              12.5:1                                         125.0                                                                               20.0 8.0   5.0  0.06                                                                               0.25                                                                               0.31                                                                              1.5:1                                    test against a mixed-culture in TSB medium                                     MIC   250.0                                                                               12.5 8.0   5.0  0.03                                                                               0.40                                                                               0.43                                                                              1.5:1                                    MBCId 250.0                                                                               50.0 31.0  20.0 0.12                                                                               0.40                                                                               0.52                                                                              1.5:1                                    MBC2d 250.0                                                                               50.0 31.0  20.0 0.12                                                                               0.40                                                                               0.52                                                                              1.5:1                                    MBC6d 250.0                                                                               12.5 8.0   5.0  0.03                                                                               0.40                                                                               0.43                                                                              1.5:1                                    __________________________________________________________________________      Compound A = Octhilinone                                                       Compound B = 5Bromo-5-nitro-1,3-dioxane                                        The synergistic ratios of compound A:compound B range from 100:1 to            1:12.5.                                                                        The preferred ratios are 1.5:1 to 1:12.5.                                

                  TABLE 4                                                          ______________________________________                                         Combination of Octhilinone and                                                 Hexahydro-1,3,5-triethyl-s-triazine                                                               calculations                                                Method of                                                                              end-point activity in ppm                                                                       Qa/    Qb/       Qa:                                  evaluation                                                                             QA     QB      Qa   Qb   QA   QB   SI   Qb                             ______________________________________                                         test against E. coli in M9G                                                    MIC     125.0  16.0    62.0 4.0  0.50 0.25 0.75 16:1                           MBCId   250.0  125.0   62.0 16.0 0.25 0.13 0.38  4:1                           MBC4d   125.0  16.0    62.0 4.0  0.50 0.25 0.75 16:1                           MBC7d   125.0  16.0    62.0 4.0  0.50 0.25 0.75 16:1                           ______________________________________                                          Compound A = Octhilinone                                                       Compound B = Hexahydro1,3,5-triethyl-s-triazine                                The synergistic ratios of compound A:compound B range from 4:1 to 16:1.        The preferred ratios are 4:1 to 16:1.                                    

                                      TABLE 5                                      __________________________________________________________________________     Combination of Octhilinone and α-Benzoyl-α-chloroformaldoxime      Method of                                                                            end-point activity in ppm                                                                         calculations                                          evaluation                                                                           QA  QB   Qa   Qb   Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                      __________________________________________________________________________     test against E. coli in M9G medium                                             MIC   125.0                                                                              500.0                                                                                8.0 125.0                                                                               0.06                                                                               0.25                                                                               0.31                                                                               1:15                                            125.0                                                                              500.0                                                                               31.0 62.0 0.25                                                                               0.12                                                                               0.37                                                                              1:2                                              125.0                                                                              500.0                                                                               62.0 31.0 0.50                                                                               0.06                                                                               0.56                                                                              2:1                                        MBCId 250.0                                                                              500.0                                                                                4.0 250.0                                                                               0.02                                                                               0.50                                                                               0.52                                                                               1:62                                            250.0                                                                              500.0                                                                               62.0 62.0 0.25                                                                               0.12                                                                               0.37                                                                              1:1                                              250.0                                                                              500.0                                                                               125.0                                                                                2.0 0.50                                                                               0.00                                                                               0.50                                                                              62:1                                       MBC4d 125.0                                                                              500.0                                                                                8.0 125.0                                                                               0.06                                                                               0.25                                                                               0.31                                                                               1:15                                            125.0                                                                              500.0                                                                               31.0 62.0 0.25                                                                               0.12                                                                               0.37                                                                              1:2                                              125.0                                                                              500.0                                                                               62.0 31.0 0.50                                                                               0.06                                                                               0.56                                                                              2:1                                        MBC7d 125.0                                                                              500.0                                                                                8.0 125.0                                                                               0.06                                                                               0.25                                                                               0.31                                                                               1:15                                            125.0                                                                              500.0                                                                               31.0 62.0 0.25                                                                               0.12                                                                               0.37                                                                              1:2                                              125.0                                                                              500.0                                                                               62.0 31.0 0.50                                                                               0.06                                                                               0.56                                                                              2:1                                        test against C. albicans in TSB medium                                         MIC    1.0                                                                               2000.0                                                                               0.3 31.0 0.25                                                                               0.02                                                                               0.27                                                                               1:100                                     MBC2d  2.0                                                                               2000.0                                                                               0.3 31.0 0.13                                                                               0.02                                                                               0.15                                                                               1:100                                     MBC6d  1.0                                                                               2000.0                                                                               0.3 31.0 0.25                                                                               0.02                                                                               0.27                                                                               1:100                                     test against E. coli in TSB medium                                             MIC   250.0                                                                              2000.0                                                                              125.0                                                                               62.0 0.50                                                                               0.03                                                                               0.53                                                                              2:1                                        MBC2d 250.0                                                                              2000.0                                                                              125.0                                                                               62.0 0.50                                                                               0.03                                                                               0.53                                                                              2:1                                        MBC6d 250.0                                                                              2000.0                                                                              125.0                                                                               62.0 0.50                                                                               0.03                                                                               0.53                                                                              2:1                                        __________________________________________________________________________      Compound A = Octhilinone                                                       Compound B = α-Benzoylα-chloroformaldoxime                         The synergistic ratios of compound A:compound B range from 62:1 to 1:100.      The preferred ratios are 2:1 to 1:2.                                     

                                      TABLE 6                                      __________________________________________________________________________     Combination of Octhilinone and Benzylbromoacetate                              Method of                                                                            end-point activity in ppm                                                                           calculations                                        evaluation                                                                           QA   QB    Qa   Qb   Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                    __________________________________________________________________________     test against C. albicans in TSB medium                                         MIC    2.5 12.5   0.1 3.1  0.03                                                                               0.25                                                                               0.28                                                                                1:40                                          2.5 12.5   0.3 1.6  0.12                                                                               0.13                                                                               0.25                                                                                1:5                                    test against a mixed culture in TSB medium                                     MIC   250.0                                                                               100.0 62.0 50.0 0.25                                                                               0.50                                                                               0.75                                                                              1.2:1                                    MBC2d 250.0                                                                               200.0 62.0 50.0 0.25                                                                               0.25                                                                               0.50                                                                              1.2:1                                    MBC6d 250.0                                                                               200.0 62.0 50.0 0.25                                                                               0.25                                                                               0.50                                                                              1.2:1                                    test against E. coli in M9G medium                                             MIC   125.0                                                                               12.5  31.0 1.6  0.25                                                                               0.13                                                                               0.38                                                                               20:1                                          125.0                                                                               12.5  16.0 3.1  0.13                                                                               0.25                                                                               0.38                                                                                5:1                                    MBCId 125.0                                                                               25.0  62.0 1.6  0.50                                                                               0.06                                                                               0.56                                                                               40:1                                          125.0                                                                               25.0  31.0 3.1  0.25                                                                               0.12                                                                               0.37                                                                               10:1                                          125.0                                                                               25.0  16.0 12.5 0.13                                                                               0.50                                                                               0.63                                                                              1.2:1                                    __________________________________________________________________________      Compound A = Octhilinone                                                       Compound B = Benzylbromoacetate                                                The synergistic ratios of compound A:compound B range from 40:1 to 1:40.       The preferred ratios are 10:1 to 1:5.                                    

                                      TABLE 7                                      __________________________________________________________________________     Combination of Octhilinone and p-Chloro-m-xylenol                              Method of                                                                            end-point activity in ppm                                                                         calculations                                          evaluation                                                                           QA   QB   Qa   Qb  Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                      __________________________________________________________________________     test against E. coli in M9G medium                                             MIC   125.0                                                                               250.0                                                                                8.0 125.0                                                                              0.06                                                                               0.50                                                                               0.56                                                                               1:15                                            125.0                                                                               250.0                                                                               62.0 62.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              1:1                                        MBCId 250.0                                                                               250.0                                                                                8.0 125.0                                                                              0.03                                                                               0.50                                                                               0.53                                                                               1:15                                            250.0                                                                               250.0                                                                               62.0 62.0                                                                               0.25                                                                               0.25                                                                               0.50                                                                              1:1                                        MBC4d 125.0                                                                               250.0                                                                                8.0 125.0                                                                              0.06                                                                               0.50                                                                               0.56                                                                               1:15                                            125.0                                                                               250.0                                                                               62.0 62.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              1:1                                        MBC7d 125.0                                                                               250.0                                                                                8.0 125.0                                                                              0.06                                                                               0.50                                                                               0.56                                                                               1:15                                            125.0                                                                               250.0                                                                               62.0 62.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              1:1                                        test against C. albicans in TSB medium                                         MIC    2.5  62.0                                                                                1.3  8.0                                                                               0.50                                                                               0.13                                                                               0.63                                                                                1:6.2                                    test against E. coli in TSB medium                                             MIC    125.0                                                                              125.0                                                                               62.0 31.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              2:1                                        MBCId 125.0                                                                               125.0                                                                               62.0 31.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              2:1                                        MBC2d 125.0                                                                               125.0                                                                               62.0 31.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              2:1                                        __________________________________________________________________________      Compound A = Octhilinone                                                       Compound B = pChloro-m-xylenol                                                 The synergistic ratios of compound A:compound B range from 2:1 to 1:15.        The preferred ratios are 2:1 to 1:15.                                    

                                      TABLE 8                                      __________________________________________________________________________     Combination of Octhilinone and Bis-(2-hydroxy-5-chlorophenyl)sulfide           Method of                                                                            end-point activity in ppm                                                                         calculations                                          evaluation                                                                           QA   QB   Qa   Qb  Qa/QA                                                                              Qb/QB                                                                              SI Qa:Qb                                      __________________________________________________________________________     test against E. coli in M9G medium                                             MIC   125.0                                                                               125.0                                                                               62.0 31.0                                                                               0.50                                                                               0.25                                                                               0.75                                                                              2:1                                        MBC4d 125.0                                                                               125.0                                                                               62.0 62.0                                                                               0.50                                                                               0.50                                                                               1.00                                                                              1:1                                        MBC7d 125.0                                                                               125.0                                                                               62.0 62.0                                                                               0.50                                                                               0.50                                                                               1.00                                                                              1:1                                        test against C. albicans in TSB medium                                         MIC   0.3  31.0 0.1  8.0 0.26                                                                               0.26                                                                               0.52                                                                              1:100                                            0.3  31.0 0.2  2.0 0.52                                                                               0.06                                                                               0.58                                                                              1:10                                       MBCId 0.6  31.0 0.1  8.0 0.13                                                                               0.26                                                                               0.39                                                                              1:100                                            0.6  31.0 0.2  2.0 0.26                                                                               0.06                                                                               0.32                                                                              1:10                                       MBC4d 0.6  31.0 0.1  8.0 0.13                                                                               0.26                                                                               0.39                                                                              1:100                                            0.6  31.0 0.2  2.0 0.26                                                                               0.06                                                                               0.32                                                                              1:10                                       __________________________________________________________________________      Compound A = Octhilinone                                                       Compound B = Bis(2-hydroxy-5-chlorophenyl)sulfide                              The synergistic ratios of compound A:compound B range from 2:1 to 1:100.       The preferred ratios are 2:1 to 1:10.                                    

                  TABLE 9                                                          ______________________________________                                         Combination of Octhilinone and p-Tolyldiiodomethylsulfone                      Compound A = Octhilinone                                                       Compound B =  -p-Tolyldiiodomethylsulfone                                                        calculations                                                 Method of                                                                              end-point activity in ppm                                                                      Qa/    Qb/                                             evaluation                                                                             QA     QB     Qa   Qb   QA   QB   Sl   Qa:Qb                           ______________________________________                                         test against E. coli in TSB medium                                             MIC     250.0  100.0   2.0 50.0 0.01 0.50 0.51  1:25                                   250.0  100.0  125.0                                                                               0.8  0.50 0.01 0.51 150:1                           MBC2d   250.0  100.0   2.0 50.0 0.01 0.50 0.51  1:25                                   250.0  100.0  125.0                                                                               0.8  0.50 0.01 0.51 150:1                           MBC6d   250.0  100.0   2.0 50.0 0.01 0.05 0.51  1:25                                   250.0  100.0  125.0                                                                               0.8  0.50 0.01 0.51 150:1                           test against C. albicans in TSB medium                                         MIC      4.0    6.2    0.3 0.8  0.06 0.13 0.19  1:3.2                                   4.0    6.2    0.5 0.4  0.13 0.06 0.19  1.2:1                                   4.0    6.2    1.0 0.2  0.25 0.03 0.28  5:1                            MBC2d    4.0    6.2    0.3 0.8  0.06 0.13 0.19  1:3.2                                   4.0    6.2    0.5 0.4  0.13 0.06 0.19  1.2:1                                   4.0    6.2    2.0 0.2  0.50 0.03 0.53  10:1                           MBC6d    4.0    6.2    0.3 0.8  0.06 0.13 0.19  1:3.2                                   4.0    6.2    0.5 0.4  0.13 0.06 0.19  1.2:1                                   4.0    6.2    1.0 0.2  0.25 0.03 0.28  5:1                            test against E. coli in M9G medium                                             MBC2d   125.0   25.0   62.0                                                                               6.2  0.50 0.25 0.75  10:1                                   125.0   25.0   31.0                                                                               12.5 0.25 0.50 0.75  2.5:1                          test against a mixed culture in TSB medium                                     MIC     250.0   50.0   31.0                                                                               12.5 0.12 0.25 0.37  2.5:1                          MBCld   250.0  200.0   62.0                                                                               25.0 0.25 0.13 0.37  2.5:1                          MBC2d   250.0  200.0   62.0                                                                               25.0 0.25 0.13 0.37  2.5:1                          MBC6d   250.0   50.0   31.0                                                                               12.5 0.12 0.25 0.37  2.5:1                          ______________________________________                                          The synergistic ratios of compound A:compound B range from 150:1 to 1:25.      The preferred ratios are 2.5:1 to 1:25.                                  

                  TABLE 10                                                         ______________________________________                                         Combination of Octhilinone and                                                 3-lodo-2-propynylbutylcarbamate                                                Compound A = Octhilinone                                                       Compound B = 3-lodo-2-propynylbutylcarbamate                                                     calculations                                                 Method of                                                                              end-point activity in ppm                                                                      Qa/    Qb/                                             evaluation                                                                             QA     QB     Qa   Qb   QA   QB   Sl   Qa:Qb                           ______________________________________                                         test against E. coli in TSB medium                                             MIC     250.0  200.0  125.0                                                                               100.0                                                                               0.50 0.50 1.00 1.2:1                           MBC2d   250.0  200.0  125.0                                                                               100.0                                                                               0.50 0.50 1.00 1.2:1                           MBC6d   250.0  200.0  125.0                                                                               100.0                                                                               0.50 0.50 1.00 1.2:1                           test against C. albicans in TSB medium                                         MIC      2.0    6.2    0.3  1.6 0.13 0.26 0.38   1:6.2                                  2.0    6.2    1.0  0.2 0.50 0.03 0.53   5:1                           MBC2d    2.0    6.2    0.5  1.6 0.25 0.26 0.51   1:3.1                                  2.0    6.2    1.0  0.2 0.50 0.03 0.53   5:1                           MBC6d    2.0    6.2    0.5  1.6 0.25 0.26 0.51   1:3.1                                  2.0    6.2    1.0  0.2 0.50 0.03 0.53   5:1                           test against E. coli M9G medium                                                M9G      62.0   3.1    2.0  1.6 0.03 0.52 0.55 1.2:1                           MBC2d    62.0   50.0   31.0                                                                                3.1 0.50 0.06 0.56  10:1                                    62.0   50.0   2.0  25.0                                                                               0.03 0.50 0.53   1:12.5                        test against a mixed-culture in TSB medium                                     MIC     250.0  200.0   31.0                                                                               100.0                                                                               0.12 0.50 0.62   1:3.1                         MBCld   250.0  400.0   31.0                                                                               100.0                                                                               0.12 0.25 0.37   1:3.1                         MBC2d   250.0  400.0   31.0                                                                               100.0                                                                               0.12 0.25 0.37   1:3.1                         MBC4d   250.0  200.0   31.0                                                                               100.0                                                                               0.12 0.50 0.62   1:3.1                         ______________________________________                                          The synergistic ratios of compound A:compound B range from 10:1 to 1:12.5      The preferred ratios are 5:1 to 1:3.1.                                   

                  TABLE 11                                                         ______________________________________                                         Combination of Octhilinone and 5-Hydroxypoly(methyleneoxy)-                    methyl-1-aza-3,7-dioxabicyclo(3,3,0)octane                                     Compound A = Octhilinone                                                       Compound B = 5-Hydroxypoly(methyleneoxy)-                                      methyl-1-aza-3,7-dioxabicyclo(3,3,0)octane                                     Method                  calculations                                           of eval-                                                                               end-point activity in ppm                                                                      Qa/    Qb/                                             ation  QA     QB      Qa   Qb   QA   QB   Sl   Qa:Qb                           ______________________________________                                         test against E. coli in TSB medium                                             MIC    125.0   250.0  62.0 125.0                                                                               0.50 0.50 1.00 1.2                             MBC2d  125.0   500.0  31.0 250.0                                                                               0.25 0.50 0.75 1:8                                    125.0   500.0  62.0 125.0                                                                               0.50 0.25 0.75 1:2                             MBC6d  125.0   500.0  8.0  250.0                                                                               0.06 0.50 0.56 1:31                                   125.0   500.0  62.0 125.0                                                                               0.50 0.25 0.75 1:2                             test against C. albicans in TSB medium                                         MIC     2.0   1000.0  0.3   31.0                                                                               0.13 0.03 0.16 1:125                                   2.0   1000.0  1.0   0.5 0.50 0.00 0.50 2:1                             MBC2d   2.0   1000.0  0.3   31.0                                                                               0.13 0.03 0.16 1:125                                   2.0   1000.0  1.0   4.0 0.50 0.00 0.50 1:4                             MBC6d   2.0   1000.0  0.3   31.0                                                                               0.13 0.03 0.16 1:125                                   2.0   1000.0  1.0   4.0 0.50 0.00 0.50 1:4                             test against E. coli M9G medium                                                MIC    125.0   62.0   31.0  31.0                                                                               0.25 0.50 0.75 1:1                             MBCld  125.0   125.0  62.0  31.0                                                                               0.50 0.25 0.75 2:1                                    125.0   125.0  16.0  62.0                                                                               0.13 0.50 0.62 1:4                             test against a mixed-culture in TSB medium                                     MIC    250.0   500.0  31.0 125.0                                                                               0.12 0.25 0.37 1:4                             MBCld  250.0  1000.0  31.0 125.0                                                                               0.12 0.13 0.25 1:4                             MBC2d  250.0   500.0  31.0 125.0                                                                               0.12 0.25 0.37 1:4                             MBC6d  250.0   500.0  31.0 125.0                                                                               0.12 0.25 0.37 1:4                             ______________________________________                                          The synergistic ratios of compound A:compound B range from 2:1 to 1:125.       The preferred ratios are 1:4 to 1:31.                                    

                  TABLE 12                                                         ______________________________________                                         Combination of Octhilinone and Dipropylamine ether                             Compound A = Octhilinone                                                       Compound B = Dipropylamine ether                                               Method              calculations                                               of eval-                                                                              end-point activity in ppm                                                                       Qa/    Qb/                                             uation QA     QB      Qa   Qb   QA   QB   Sl   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MIC    125.0  31.0    2.0  16.0 0.02 0.52 0.53 1:8                                    125.0  31.0    8.0  8.0  0.06 0.26 0.32 1:1                                    125.0  31.0    62.0 2.0  0.50 0.06 0.56 31:1                            MBCld  250.0  62.0    62.0 8.0  0.25 0.13 0.38 8:1                                    250.0  62.0    2.0  31.0 0.01 0.50 0.51  1:16                           MBC4d  125.0  31.0    16.0 16.0 0.13 0.52 0.64 1:1                                    125.0  31.0    62.0 2.0  0.50 0.06 0.56 31:1                            MBC7d  125.0  31.0    2.0  16.0 0.02 0.52 0.53 1:8                                    125.0  31.0    62.0 2.0  0.50 0.06 0.56 31:1                            test against C. albicans in TSB medium                                         MIC     1.3   125.0   0.6  16.0 0.50 0.13 0.62  1:25                           test against E. coli in TSB medium                                             MIC    125.0  50.0    31.0 6.2  0.25 0.12 0.37 5:1                                    125.0  50.0    8.0  12.5 0.06 0.25 0.31   1:1.6                         MBCld  125.0  50.0    31.0 6.2  0.25 0.12 0.37 5:1                                    125.0  50.0    16.0 12.5 0.13 0.25 0.38 1.3:1                           MBC2d  125.0  50.0    31.0 6.2  0.25 0.12 0.37 5:1                                    125.0  50.0    16.0 12.5 0.13 0.25 0.38 1.3:1                           test against a mixed-culture in TSB medium                                     MIC    250.0  500.0   31.0 50.0 0.12 0.10 0.22   1:1.6                                250.0  500.0   62.0 25.0 0.25 0.05 0.30 2.5:1                           MBC6d  250.0  500.0   62.0 25.0 0.25 0.05 0.30 2.5:1                           ______________________________________                                          The synergistic ratios of compound A:compound B range from 8:1 to 1:25.        The preferred ratios are 2.5:1 to 1:6.                                   

                  TABLE 13                                                         ______________________________________                                         Combination of Octhilinone and Dodecylamine                                    Compound A = Octhilinone                                                       Compound B = Dodecylamine                                                      Method             calculations                                                of eval-                                                                              end-point activity in ppm                                                                      Qa/                                                     uation QA     QB     Qa   Qb   QA   Qb/QB Sl   Qa:Qb                           ______________________________________                                         test against a mixed-culture in TSB medium                                     MIC    250.0  100.0  31.0 25.0 0.12 0.25  0.37 1.2:1                           MBCld  250.0  200.0  31.0 25.0 0.12 0.13  0.25 1.2:1                           MBC2d  250.0  100.0  31.0 25.0 0.12 0.25  0.37 1.2:1                           MBC6d  250.0  100.0  31.0 25.0 0.12 0.25  0.37 1.2:1                           test against E. coli in M9G medium                                             MIC    125.0   25.0  62.0 6.2  0.50 0.25  0.75  10:1                                  125.0   25.0  31.0 12.5 0.25 0.50  0.75 2.5:1                           MBCld  125.0   25.0  31.0 12.5 0.25 0.50  0.75 2.5:1                           MBC2d  125.0   25.0  31.0 12.5 0.25 0.50  0.75 2.5:1                                  125.0   25.0  62.0 6.2  0.50 0.25  0.75  10:1                           ______________________________________                                          The synergistic ratios of compound A:compound B range from 10:1 to 1.2:1.      The preferred ratios are 2.5:1 to 1.2:1.                                 

                  TABLE 14                                                         ______________________________________                                         Combination of Octhilinone and N-(hydroxymethyl)-N'-                           (1,3-di(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl)-N'-                         (hydroxymethyl)urea                                                            Compound A = Octhilinone                                                       Compound B = N-(hydroxymethyl)-N'-(1,3-                                        di(hydroxymethyl)-2,5-dioxo-4-                                                 imidazolidinyl-N'-(hydroxymethyl)urea                                          Method              calculations                                               of eval-                                                                              end-point activity in ppm                                                                       Qa/    Qb/                                             uation QA     QB      Qa   Qb   QA   QB   Sl   Qa:Qb                           ______________________________________                                         test against a mixed-culture in TSB medium                                     MIC    250.0   500.0  31.0 250.0                                                                               0.12 0.50 0.62 1:8                             MBCld  250.0  1000.0  62.0 500.0                                                                               0.25 0.50 0.75 1:8                             MBC2d  250.0  1000.0  31.0 250.0                                                                               0.12 0.25 0.37 1:8                             MBC6d  250.0  1000.0  31.0 250.0                                                                               0.12 0.25 0.37 1:8                             test against E. coli in M9G medium                                             MIC    125.0   125.0  31.0  62.0                                                                               0.25 0.50 0.75 1:2                             MBCld  250.0   500.0  16.0 125.0                                                                               0.06 0.25 0.31 1:8                                    250.0   500.0  31.0  62.0                                                                               0.12 0.12 0.25 1:2                                    250.0   500.0  62.0  31.0                                                                               0.25 0.06 0.31 2:1                             MBC4d  125.0   125.0  31.0  62.0                                                                               0.25 0.50 0.75 1:2                             MBC7d  125.0   125.0  31.0  62.0                                                                               0.25 0.50 0.75 1:2                             test against E. coli in TSB medium                                             MIC    125.0   500.0  62.0 250.0                                                                               0.50 0.50 1.00 1:4                             MBC2d  125.0  1000.0  31.0 500.0                                                                               0.25 0.50 0.75  1:16                                  125.0  1000.0  62.0 250.0                                                                               0.50 0.25 0.75 1:4                             MBC6d  125.0  1000.0   8.0 500.0                                                                               0.06 0.50 0.56  1:62                                  125.0  1000.0  62.0 250.0                                                                               0.50 0.25 0.75 1:4                             ______________________________________                                          The synergistic ratios of compound A:compound B range from 2:1 to 1:62.        The preferred ratios are 1:2 to 1:8.                                     

                  TABLE 15                                                         ______________________________________                                         Combination of Octhilinone and 1-(3-Chloroallyl)-3,5,7-triaza-1-               azoniaadamantane chloride                                                      Compound A = Octhilinone                                                       Compound B = 1-(3-Chloroallyl)-3,5,7-triaza-1-                                 azoniaadamantane chloride                                                      Method                  calculations                                           of eval-                                                                              end-point activity in ppm                                                                       Qa/    Qb/                                             uation QA     QB      Qa   Qb   QA   QB   Sl   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MIC    125.0  125.0   16.0  62.0                                                                               0.13 0.50 0.62 1:4                                    125.0  125.0   62.0  31.0                                                                               0.50 0.25 0.74 2:1                             MBCld  250.0  1000.0  62.0 125.0                                                                               0.25 0.13 0.37 1:2                                    250.0  1000.0  31.0 250.0                                                                               0.12 0.25 0.37 1:8                                    250.0  1000.0  8.0  500.0                                                                               0.03 0.50 0.53   1:62.5                        MBC4d  125.0  125.0   16.0  62.0                                                                               0.13 0.50 0.62 1:4                                    125.0  125.0   62.0  31.0                                                                               0.50 0.25 0.74 2:1                             MBC7d  125.0  125.0   16.0  62.0                                                                               0.13 0.50 0.62 1:4                                    125.0  125.0   62.0  31.0                                                                               0.50 0.25 0.74 2:1                             ______________________________________                                          The synergistic ratios of compound A:compound B range from 2:1 to 1:62.5.      The preferred ratios are 2:1 to 1:4.                                     

                  TABLE 16                                                         ______________________________________                                         Combination of Octhilinone and 1,2-Dibromo-2,4-dicyanobutane                   Compound A = Octhilinone                                                       Compound B = 1,2-Dibromo-2,4-dicyanobutane                                     Method             calculations                                                of eval-                                                                              end-point activity in ppm                                                                      Qa/    Qb/                                              uation QA     QB     Qa   Qb   QA   QB   Sl    Qa:Qb                           ______________________________________                                         test against E. coli in TSB medium                                             MIC    125.0  250.0  31.0 50.0 0.25 0.20 0.45 1:1.6                            MBC2d  125.0  250.0  62.0 50.0 0.50 0.20 0.70 1.2:1                            MBC6d  125.0  250.0  62.0 50.0 0.50 0.20 0.70 1.2:1                            test against C. albicans in TSB medium                                         MIC     2.5    62.0  1.3  4.0  0.50 0.06 0.56 1:3.2                                    2.5    62.0  0.6  16.0 0.25 0.26 0.51 1:25                             test against E. coli in M9G medium                                             MIC     62.0   25.0  31.0 3.1  0.50 0.12 0.62 10:1                                     62.0   25.0  8.0  6.2  0.13 0.25 0.38 1.2:1                                    62.0   25.0  4.0  12.5 0.06 0.50 0.56 1:3.2                            MBCld   62.0  100.0  31.0 3.1  0.50 0.03 0.53 1:1.6                                    62.0  100.0  8.0  12.5 0.13 0.13 0.25 1:1.6                                    62.0  100.0  4.0  50.0 0.06 0.50 0.56  1:12.5                          test against a mixed-culture in TSB medium                                     MIC    250.0   50.0  16.0 25.0 0.06 0.50 0.56 1:1.6                            MBCld  250.0  400.0  62.0 50.0 0.25 0.13 0.37 1.2:1                            MBC2d  250.0  200.0  31.0 50.0 0.12 0.25 0.37 1:1.6                            MBC6d  250.0  200.0  16.0 25.0 0.06 0.13 0.19 1:1.6                            ______________________________________                                          The synergistic ratios of compound A:compound B range from 10:1 to 1:25.       The preferred ratios are 1.2:1 to 1:3.2.                                 

                  TABLE 17                                                         ______________________________________                                         Combination of Octhilinone and N,N-dimethyl-N'-phenyl-N'-                      fluorodichloromethylthio)sulfamide                                             Compound A = Octhilinone                                                       Compound B = N,N-dimethyl-N'-phenyl-N'-                                        (fluorodichloromethylthio)sulfamide                                                              calculations                                                 Method of                                                                              end-point activity in ppm                                                                      Qa/    Qb/                                             evaluation                                                                             QA     QB     Qa   Qb   QA   QB   SI   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MIC     125.0  500.0  62.0  62.0                                                                               0.50 0.12 0.62 1:1                                     125.0  500.0  31.0 125.0                                                                               0.25 0.25 0.50 1:4                             MBC1d   125.0  500.0  62.0  62.0                                                                               0.50 0.12 0.62 1:1                             test against C. albicans in TSB medium                                         MIC      2.5   500.0   1.3 125.0                                                                               0.50 0.25 0.75  1:100                          ______________________________________                                          The synergistic ratios of compound A:compound B range from 1:1 to 1:100.       The preferred ratios are 1:1 to 1:4.                                     

                  TABLE 18                                                         ______________________________________                                         Combination of Octhilinone and N,N'-di(hydroxymethyl)-5,5'-                    dimethylhydantoin                                                              Compound A = Octhilinone                                                       Compound B = N,N'-di(hydroxymethyl)-5,5'-                                      dimethylhydantoin                                                              Method              calculations                                               of evalu-                                                                             end-point activity in ppm                                                                       Qa/    Qb/                                             ation  QA     QB      Qa   Qb   QA   QB   SI   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MIC    125.0   250.0   8.0 125.0                                                                               0.06 0.50 0.56  1:15                           MBC1d  125.0   250.0   8.0 125.0                                                                               0.06 0.50 0.56  1:15                           test against mixed-culture in TSB medium                                       MIC    250.0  2000.0  62.0 500.0                                                                               0.25 0.25 0.50 1:8                             MBC1d  250.0  2000.0  62.0 500.0                                                                               0.25 0.25 0.50 1:8                             MBC2d  250.0  2000.0  62.0 500.0                                                                               0.25 0.25 0.50 1:8                             MBC6d  250.0  2000.0  62.0 500.0                                                                               0.25 0.25 0.50 1:8                             ______________________________________                                          The synergistic ratios of compound A:compound B range from 1:8 to 1:15.        The preferred ratios are 1:8 to 1:15.                                    

                  TABLE 19                                                         ______________________________________                                         Combination of Octhilinone and 2-Bromo-2-nitropropanediol                      Compound A = Octhilinone                                                       Compound B = 2-Bromo-2-nitropropanediol                                                          calculations                                                 Method of                                                                              end-point activity in ppm                                                                      Qa/    Qb/                                             evaluation                                                                             QA     QB     Qa   Qb   QA   QB   SI   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MBC1d   125.0   8.0   16.0 4.0  0.13 0.50 0.63 4:1                             test against C. albicans in TSB medium                                         MIC      2.5   62.0   0.1  31.0 0.03 0.50 0.53  1:400                                   2.5   62.0   0.6  16.0 0.25 0.26 0.51  1:25                                    2.5   62.0   1.3  5.0  0.50 0.08 0.58 1:4                             test against a mixed-culture in TSB medium                                     MIC     250.0   4.0   4.0  2.0  0.02 0.50 0.52 2:1                             MBC1d   250.0  32.0   16.0 8.0  0.06 0.25 0.31 2:1                             MBC2d   250.0  16.0   8.0  4.0  0.03 0.25 0.28 2:1                             MBC6d   250.0   8.0   4.0  2.0  0.02 0.25 0.27 2:1                             ______________________________________                                          The synergistic ratios of compound A:compound B range from 4:1 to 1:400.       The preferred ratios are 4:1 to 1:4.                                     

                  TABLE 20                                                         ______________________________________                                         Combination of Octhilinone and Methylene-bis-thiocyanate                       Compound A = Octhilinone                                                       Compound B = Methylene-bis-thiocyanate                                                           calculations                                                 Method of                                                                              end point activity in ppm                                                                      Qa/    Qb/                                             evaluation                                                                             QA     QB     Qa   Qb   QA   QB   SI   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MIC     125.0  4.0    16.0 2.0  0.13 0.50 0.63 8:1                                     125.0  4.0    62.0 1.0  0.50 0.25 0.75 62:1                            MBC1d   250.0  31.0   62.0 16.0 0.25 0.52 0.77 4:1                                     250.0  31.0   125.0                                                                               4.0  0.50 0.13 0.63 31:1                            MBC4d   125.0  4.0    31.0 2.0  0.25 0.50 0.75 16:1                            MBC7d   125.0  4.0    31.0 2.0  0.25 0.50 0.75 16:1                                    125.0  4.0    62.0 1.0  0.50 0.25 0.75 62:1                            test against C. albicans in TSB medium                                         MIC      2.5   6.2     0.2 3.1  0.06 0.50 0.56  1:20                                    2.5   6.2     0.6 1.6  0.25 0.26 0.51   1:2.5                                  2.5   6.2     1.3 0.8  0.50 0.13 0.63 1.6:1                           test against a mixed-culture in TSB medium                                     MBC1d   250.0  100.0  25.0 50.0 0.10 0.50 0.60 1:2                             MBC2d   250.0  100.0  25.0 50.0 0.10 0.50 0.60 1:2                             MBC6d   250.0   12.5   3.1 6.2  0.01 0.50 0.51 1:2                             ______________________________________                                          The synergistic ratios of compound A:compound B range from 62:1 to 1:20.       The preferred ratios are 16:1 to 1:2.                                    

                  TABLE 21                                                         ______________________________________                                         Combination of Octhilinone and 2,4-Dichlorobenzyl alcohol                      Compound A = Octhilinone                                                       Compound B = 2,4-Dichlorobenzyl alcohol                                                          calculations                                                 Method of                                                                              end-point activity in ppm                                                                      Qa/    Qb/                                             evaluation                                                                             QA     QB     Qa   Qb   QA   QB   SI   Qa:Qb                           ______________________________________                                         test against E. coli in M9G medium                                             MIC     125.0   62.0  62.0 16.0 0.50 0.26 0.75 4:1                             MBC1d   250.0  125.0  31.0 62.0 0.12 0.50 0.62 1:2                                     250.0  125.0  62.0 31.0 0.25 0.25 0.50 2:1                             MBC4d   125.0  125.0  31.0 62.0 0.25 0.50 0.75 1:2                                     125.0  125.0  62.0 31.0 0.50 0.25 0.75 2:1                             MBC7d   125.0  125.0  31.0 62.0 0.25 0.50 0.75 1:2                                     125.0  125.0  62.0 16.0 0.50 0.13 0.62 4:1                             test against C. albicans in TSB medium                                         MIC      2.5   125.0   1.3  8.0 0.50 0.06 0.56   1:6.2                         ______________________________________                                          The synergistic ratios of compound A:compound B range from 4:1 to 1:6.2.       The preferred ratios are 4:1 to 1:2.                                     

                  TABLE 22                                                         ______________________________________                                         Combination of Octhilinone Sodium dichlorophene                                Compound A = Octhilinone                                                       Compound B = Sodium dichlorophene                                              Method of                                                                              end-point activity in ppm                                                                        calculations                                         evaluation                                                                             QA      QB     Qa   Qb    Qa/QA Qb/QB SI                               ______________________________________                                         test against E. coli in M9G medium                                             MIC     125.0   16.0   125.0                                                                               16.0  NA    NA    NA                               MBC1d   250.0   16.0   250.0                                                                               16.0  NA    NA    NA                               MBC4d   125.0   16.0   125.0                                                                               16.0  NA    NA    NA                               MBC7d   125.0   16.0   125.0                                                                               16.0  NA    NA    NA                               test against E. coli in TSB medium                                             MIC     125.0   62.0   125.0                                                                               62.0  NA    NA    NA                               MBC1d   125.0   62.0   125.0                                                                               62.0  NA    NA    NA                               test against C. albicans in TSB medium                                         MIC      2.5    50.0    1.3 25.0  0.50  0.50  1.00                             ______________________________________                                          NA = not applicable because it is not endpoint of activity.              

As can be seen by review of Tables 1-21, the compositions demonstrate synergistic antimicrobial activities as measured by minimum inhibitory concentrations (MIC) and synergistic biocidal activity as measured by minimum biocidal concentrations (MBC), and show surprisingly greater activity than the algebraic sum of the individual ingredients which make up the respective composition.

In contrast, an example of non-synergistic combination of octhilinone and sodium dichlorophene is in Table 22. In this example of non-synergism, the antibacterial activities of either octhilinone or sodium dichlorophene as measured by the activities against E. coli are not affected by the presence or the absence of the other component in the combination. It is also not antagonistic because no loss of activity of either component in the combination was detected. The antifungal activity, as measured by activity against C. albicans, indeed increased as a result of the combination. The increased activity, however, is merely additive because the synergy index is 1.

The synergistic activities in most cases are applicable to bacteria, fungi, and a mixture of bacteria and fungi. Thus, the combinations not only lower the use-level of biocide but also broaden the spectrum of activity. This is especially useful in situations where either component alone does not achieve the best results due to weak activity against certain organisms. For octhilinone combinations, the synergistic activity against Gram-negative bacteria is most significant in situations where both bacteria and fungi are present in the system.

Another example is provided below to demonstrate the advantage of using octhilinone-containing compositions. In this example, a combination of octhilinone and 5-hydroxypoly(methyleneoxy)-methyl-1-aza-3,7-dioxabicyclo(3,3,0)octane (DBO) was evaluated for the control of fouling bacteria and fungi in a metalworking fluid. The test was a 4-week multiple challenge efficacy test. Octhilinone, DBO, and the combination of octhilinone and DBO were added to specified concentrations into 50 ml use dilution of the metalworking fluid in 4 oz. jars. Each jar was then inoculated weekly with a mixed culture of bacteria and fungi isolated from naturally contaminated metalworking fluid to make final concentration of about 2×10⁶ fungi and 2×10⁷ bacteria per ml of fluid. The viable counts were determined 7 days after each inoculation by 10-fold serial dilutions and platings on Trypicase Soy Agar (Difco) for bacteria and on Rose Bengal Agar with 100 ppm chloramphenicol (Oxoid) for fungi. Results of such tests are shown in Table 23. Rating of efficacy is based on generally accepted criteria in the metalworking fluid industry that >10⁵ bacteria or 10³ fungi per ml failed the efficacy test, and less than 10⁵ bacteria and 10³ fungi passed the test. When a biocide passes all 4 weekly challenge tests, it will effectively preserve the metalworking fluid. It is evident after examining Table 24 that a mixture of octhilinone and DBO preferably at ratios from 1:4 to 1:31, provides a strong synergism and effective control of bacteria, fungi, and the mixed culture of bacteria and fungi. In fact, either octhilinone or DBO is not used as a general biocide in preserving metalworking fluid due to high dosage requirement and thereby cost disadvantage. Now, with the synergistic combination of octhilinone and DBO they can be used effectively as a general biocide for preserving metalworking fluids.

                  TABLE 23                                                         ______________________________________                                         Efficacy Test on Combinations of Octhilinone and DBO                           in a Metalworking Fluid                                                        Treatment                                                                      Sample                                                                               Octhilinone                                                                              DBO      Efficacy*                                             Nos.  ppm a.i.  ppm a.i. 1 Wk. 2 Wks.                                                                               3 Wks.                                                                               4 Wks.                              ______________________________________                                         1     0          0       4     4     4     4                                   2     0         125      2     2     4     4                                   3     0         250      2     2     4     4                                   4     0         500      2     2     2     4                                   5     0         750      0     2     2     4                                   6     0         1000     0     0     0     2                                   7     0         1250     0     0     0     0                                   8     4          0       3     4     4     4                                   9     8          0       3     3     3     4                                   10    16         0       3     3     3     4                                   11    32         0       3     3     3     3                                   12    64         0       3     3     3     3                                   13    4         250      0     0     2     4                                   14    8         250      0     0     0     0                                   15    16        250      0     0     0     0                                   16    32        250      0     0     0     0                                   17    64        250      0     0     0     0                                   18    4         500      0     0     2     2                                   19    8         500      0     0     0     0                                   20    16        500      0     0     0     0                                   21    32        500      0     0     0     0                                   22    64        500      0     0     0     0                                   23    4         750      0     0     0     0                                   24    8         750      0     0     0     0                                   25    16        750      0     0     0     0                                   26    32        750      0     0     0     0                                   27    64        750      0     0     0     0                                   ______________________________________                                          *4 = failed both bacteria (>10.sup.5 cfu/ml) and fungi (>10.sup.3 cfu/ml)      3 = failed bacteria only                                                       2 = failed fungi only                                                          0 = passed both bacteria (<10.sup.5 cfu/ml) and fungi (<10.sup.3 cfu/ml) 

                                      TABLE 24                                     __________________________________________________________________________     Calculations for Synergy Index (SI) of Octhilinone (A) and DBO (B)             Combinations                                                                          Ratio                                                                   Sample Nos.                                                                           (a):(b)                                                                            SI for Bacteria*                                                                            SI for Fungi SI for Mixed Culture*                     __________________________________________________________________________     14     1:31                                                                               250/1000 + 8/500 = 0.26                                                                     250/1250 + 8/32 = 0.45                                                                      250/1250 + 8/500 = 0.21                   15     1:15                                                                               250/1000 + 16/500 = 0.28                                                                    250/1250 + 16/32 = 0.70                                                                     250/1250 + 16/500 = 0.23                  16     1:8 250/1000 + 32/500 = 0.31                                                                     NA**        250/2250 + 32/500 = 0.26                  17     1:4 250/1000 + 64/500 = 0.37                                                                    NA           250/1250 + 64/500 = 0.32                  18      1:125                                                                             500/1000 + 4/500 = 0.50                                                                     NA           NA                                        19     1:62                                                                               500/1000 + 8/500 = 0.51                                                                     500/1250 + 8/500 = 0.65                                                                     500/1250 + 8/500 = 0.41                   20     1:31                                                                               500/1000 + 16/500 = 0.53                                                                    500/1250 + 16/32 = 0.90                                                                     500/1250 + 16/500 = 0.43                  21     1:16                                                                               500/1000 + 32/500 =  0.56                                                                   NA           500/1250 + 32/500 = 0.46                  22     1:8 500/1000 + 64/500 = 0.62                                                                    NA           500/1250 + 64/500 = 0.52                  23      1:187                                                                             750/1000 + 4/500 = 0.75                                                                     750/1250 + 4/32 = 0.88                                                                      750/1250 + 4/500 = 0.60                   24     1:94                                                                               750/1000 + 8/500 = 0.76                                                                     NA           750/1250 + 8/500 = 0.61                   25     1:47                                                                               750/1000 + 16/500 = 0.78                                                                    NA           750/1250 + 16/500 = 0.63                  26     1:23                                                                               750/1000 + 32/500 = 0.81                                                                    NA           750/1250 + 32/500 = 0.66                  27     1:12                                                                               750/1000 + 64/500 = 0.87                                                                    NA           750/1250 + 64/500 = 0.72                  __________________________________________________________________________      *The endpoint activity of Octhilinone against bacteria and the mixed           culture was independently determined to be 500 ppm.                            **NA = Not applicable because they are not end points                     

What is claimed is:
 1. A microbicidal composition comprising a synergistic mixture the first component of which is 2-n-octyl-4-isothiazolin-3-one and the second component of which is N,N-di(hydroxymethyl)-5,5'-dimethylhydantoin; wherein the ratio of first component to second component is in the range of from about 1:8 to about 1:15.
 2. A method for inhibiting the growth of a member selected from the group consisting of bacteria, fungi, algae and mixtures thereof in a locus subject to contamination by said member, which comprises incorporating onto or into the locus, in an amount which is effective to adversely affect the growth of said member, the composition of claim
 1. 3. The method of claim 2 wherein the locus is an aqueous medium.
 4. The method of claim 3 wherein the composition is between from about 20 to about 400 ppm.
 5. The method of claim 3 wherein the composition is between from about 25 to about 200 ppm. 